1. Field of the Prior Art
The present invention relates to a device for cutting a pipe from the inside thereof by the oxy-arc cutting technique.
2. Description of the Prior Art
As one of the methods available for cutting steel, there can be cited the oxy-arc cutting method. This method uses a hollow stick electrode (hereinafter referred to as the "cutting rod") covered with a layer of flux serving the dual purpose of insulating the electrode from the work and stabilizing the arc, so that required cutting of a given work may be effected by generating an arc between the cutting rod and the work, then throwing a current of oxygen through the inner hole of the cutting rod and consequently cutting the work by utilizing the exothermic oxidation reaction caused between the steel and the oxygen. A short circuit would occur in the course of cutting if the underlying metal of the cutting rod should come into direct contact with the work. To avoid this trouble, the cutting rod is inclined at a fixed angle (less than 90.degree.) with reference to the work and is at the same time held in contact under a fixed force with the work, so that an arc may be generated and kept at a fixed length while otherwise possible short circuit is prevented through the intervention of the layer of covering flux. Under these conditions, the cutting rod is passed along the line selected for cutting to effect the desired cutting of the pipe. Thus, the cutting operation can be easily carried out and can be readily automated.
By the oxy-arc cutting method described above, a given pipe can be cut from the outside. It is extremely difficult, however, to effect required cutting by this method on a pipe buried under ground or a pipe surrounded by many other pipes or structural materials.